1. Field of the Invention
The present invention relates to a resin substrate including an insulating base material of which a principal surface includes a plurality of conductor patterns, and also relates to an electronic device including the resin substrate.
2. Description of the Related Art
Conventionally, a resin substrate has been configured by using resin with which metal particles are mixed (see International Publication No. 2013/105397 and Japanese Unexamined Patent Application Publication No. 2011-100649, for example).
A resin substrate disclosed in International Publication No. 2013/105397 is provided with a conductor pattern that configures a coil pattern. In the resin substrate, the coil pattern is configured in a portion of a resin layer in which a magnetic metal particle is mixed. Accordingly, the coil pattern, even if the coil pattern is small in size, has a larger inductance than normal inductance.
A resin substrate disclosed in Japanese Unexamined Patent Application Publication No. 2011-100649 is provided with a structure for ESD (Electro Static Discharge Damage) protection. Specifically, the resin substrate is provided with a cavity portion provided inside the resin substrate, a signal line conductor pattern on the side of a signal line, and a ground line conductor pattern on the side of a ground line, the signal line conductor pattern and the ground line conductor pattern facing each other with a distance in the cavity portion. The resin substrate includes, near the cavity portion, a resin layer in which conductive particles are mixed. The resin substrate, if a surge current flows into the signal line due to electrostatic discharge or the like, generates electric discharge between the signal line conductor pattern and the ground line conductor pattern, in the cavity portion. Accordingly, in the resin substrate, the surge current is able to be released from the signal line to the ground line.
A conventional resin substrate, since charging easily occurs depending on a resin material configuring the resin substrate, has sometimes caused electrostatic discharge damage to an electronic component and an electronic device when the electronic component is mounted on the resin substrate or when the resin substrate is mounted on the electronic device. The configuration disclosed in Japanese Unexamined Patent Application Publication No. 2011-100649, although being capable of releasing a surge current that flows into a signal line to the ground, has had difficulty in preventing charging of the resin substrate itself.
Therefore, in order to make a resin substrate difficult to be charged, a substantial electrical resistivity may be reduced while insulation in the resin substrate is maintained. Specifically, like conventional techniques, conductive particles may be mixed with resin. However, mere mixing of conductive particles and resin may increase the occurrence rate of a failure of a short circuit between conductor patterns mainly due to occasional deformation of the conductive particles, in a process of manufacturing a resin substrate.